Abstract 554: Multimerin2 Influences Vascularization Through Modulation of Perlecan
Vascular development is crucial in normal physiology and pathophysiology, and is in part orchestrated by a dynamic balance between extracellular matrix (ECM) and endothelial cells. The molecular mechanisms that govern this balance and as such play a role in the formation of new blood vessels remain largely unknown.
In order to identify new genes involved in blood vessel formation, we performed a genome-wide gene expression array analysis in Flk1+ angioblasts during mouse development using a commercial platform (Affymetrix). Multimerin2 (Mmrn2) expression was found to be upregulated in angioblasts and in the developing vasculature of zebrafish and mice.
In vitro, using immunofluorescence, Mmrn2 was detected outside of human aortic endothelial cells (HAECs), were it co-localized with the extracellular matrix components perlecan, laminin and fibronectin. Direct interaction with these proteins was confirmed using a combination of co-immunoprecipitation followed by proteomics (LC-MS), and western blot to identify possible binding partners.
Mmrn2 gain-of-function and loss-of-function in vitro studies, using Mmrn2 siRNA and adenoviral constructs likewise decreased and increased the expression of its binding partner perlecan. Perlecan is a well known modulator of the pro-angiogenic factor, FGF2, and is required for further signaling through the FGF receptor. Therefore, Mmrn2 may influence FGF2 signaling through perlecan expression and complex formation.
Subsequent in vitro studies using an adenoviral construct to induce Mmrn2 overexpression resulted in a G1-arrest in HAECs (P<0.001, N=8). In FGF2 depleted medium a G1 arrest was also observed (P<0.05, N=3), Mmrn2 overexpression combined with FGF2 depleted medium did not enhance the G1 arrest, suggesting a role of Mmrn2 in FGF2 signaling.
In addition, Mmrn2 silencing or overexpression in HAECs led to a loss of ECM organization or improved organization, respectively. In line, the binding partner of Mmrn2, perlecan, has been shown to be involved in stabilization of the ECM.
These findings suggest that Mmrn2 plays a role during blood vessel formation by binding to perlecan and the ECM, thereby modulating FGF2 signaling and ECM organization and subsequently, regulating endothelial cell proliferation.
Author Disclosures: P.E. Burgisser: None. D. Tempel: None. D. Hermkens: None. S. Schulte-Merker: None. C. Cheng: None. H.J. Duckers: None.
- © 2014 by American Heart Association, Inc.